This invention relates to a tire constituting member winding tension controlling apparatus for controlling tensile forces exerted on a tire constituting member depending on winding positions of the member onto a building drum when the member being transferred in contact with a tension pulley for winding the member about the building drum.
Recently, a pneumatic tire suitable for running at high speeds has been proposed. The tire is constructed so that a belt-like tire constituting member is spirally wound radially outwardly about a belt layer and tensile forces in a zone of the tire constituting member adjacent shoulders of the tire are larger than those in a zone adjacent an equatorial plane of the tire. Both the shoulders are thus strongly restrained to prevent radial enlargement of the shoulders due to a large mass of rubber. Such a tire constituting member capable of changing tensile forces therein as above described can be obtained, for example, by changing winding tensile forces depending on winding positions when the tire constituting member is being wound about a building drum.
An apparatus capable of controlling tensile forces depending on winding positions in such a manner has been proposed in Japanese Patent Application No. 62-98,388 (filed on Apr. 21, 1987 by the assignee of the present case). The proposed apparatus comprises a brake roller provided upstream of a building drum and in contact with a running tire constituting member, an electromagnetic brake connected with the brake roller and a program setting device having a program memorized therein for controlling the electromagnetic brake. Moreover, the apparatus further comprises a controller for feeding control signals to the electromagnetic brake through a regulator according to a program called from the program setting device when the tire constituting member arrives at a winding starting position so as to control braking force produced in the electromagnetic brake to give a tensile force depending on a winding position to the tire constituting member. The apparatus further comprises a tension detection sensor for detecting the tensile force given to the tire constituting member and providing a signal corresponding to the detected tensile force as a feed-back signal to the regulator.
However, such a tensile force controlling apparatus includes the electromagnetic brake and, durability against friction is low and the braking force can be variable only in a narrow range. Moreover, because feedback control is utilized, feed back delay will occur, when the tire constituting member is longer. Therefore, the apparatus has some room for improving accuracy in control of winding tensile forces with respect to a predetermined tensile force pattern, accuracy in response and reliability. Moreover, as the controlled state of the apparatus when winding the member cannot be always confirmed so that problems are only noticed after the elapse of long time.